Re: [tip:x86/mm] x86/tme: Detect if TME and MKTME is activated by BIOS

[Kai Huang]

On Mon, 2018-03-12 at 05:21 -0700, tip-bot for Kirill A. Shutemov
wrote:
> Commit-ID:  cb06d8e3d020c30fe10ae711c925a5319ab82c88
> Gitweb:     https://git.kernel.org/tip/cb06d8e3d020c30fe10ae711c925a5
> 319ab82c88
> Author:     Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> AuthorDate: Mon, 5 Mar 2018 19:25:50 +0300
> Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
> CommitDate: Mon, 12 Mar 2018 12:10:54 +0100
> 
> x86/tme: Detect if TME and MKTME is activated by BIOS
> 
> IA32_TME_ACTIVATE MSR (0x982) can be used to check if BIOS has
> enabled
> TME and MKTME. It includes which encryption policy/algorithm is
> selected
> for TME or available for MKTME. For MKTME, the MSR also enumerates
> how
> many KeyIDs are available.
> 
> We would need to exclude KeyID bits from physical address bits.
> detect_tme() would adjust cpuinfo_x86::x86_phys_bits accordingly.
> 
> We have to do this even if we are not going to use KeyID bits
> ourself. VM guests still have to know that these bits are not usable
> for physical address.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Link: http://lkml.kernel.org/r/20180305162610.37510-3-kirill.shutemov
> @linux.intel.com
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/intel.c | 90
> +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 90 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/intel.c
> b/arch/x86/kernel/cpu/intel.c
> index 4aa9fd379390..b862067bb33c 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -510,6 +510,93 @@ static void detect_vmx_virtcap(struct
> cpuinfo_x86 *c)
>  	}
>  }
>  
> +#define MSR_IA32_TME_ACTIVATE		0x982
> +
> +/* Helpers to access TME_ACTIVATE MSR */
> +#define TME_ACTIVATE_LOCKED(x)		(x & 0x1)
> +#define TME_ACTIVATE_ENABLED(x)		(x & 0x2)
> +
> +#define TME_ACTIVATE_POLICY(x)		((x >> 4) & 0xf)	
> /* Bits 7:4 */
> +#define TME_ACTIVATE_POLICY_AES_XTS_128	0
> +
> +#define TME_ACTIVATE_KEYID_BITS(x)	((x >> 32) & 0xf)	/
> * Bits 35:32 */
> +
> +#define TME_ACTIVATE_CRYPTO_ALGS(x)	((x >> 48) & 0xffff)	
> /* Bits 63:48 */
> +#define TME_ACTIVATE_CRYPTO_AES_XTS_128	1
> +
> +/* Values for mktme_status (SW only construct) */
> +#define MKTME_ENABLED			0
> +#define MKTME_DISABLED			1
> +#define MKTME_UNINITIALIZED		2
> +static int mktme_status = MKTME_UNINITIALIZED;
> +
> +static void detect_tme(struct cpuinfo_x86 *c)
> +{
> +	u64 tme_activate, tme_policy, tme_crypto_algs;
> +	int keyid_bits = 0, nr_keyids = 0;
> +	static u64 tme_activate_cpu0 = 0;
> +
> +	rdmsrl(MSR_IA32_TME_ACTIVATE, tme_activate);
> +
> +	if (mktme_status != MKTME_UNINITIALIZED) {
> +		if (tme_activate != tme_activate_cpu0) {
> +			/* Broken BIOS? */
> +			pr_err_once("x86/tme: configuation is
> inconsistent between CPUs\n");
> +			pr_err_once("x86/tme: MKTME is not
> usable\n");
> +			mktme_status = MKTME_DISABLED;
> +
> +			/* Proceed. We may need to exclude bits from
> x86_phys_bits. */
> +		}
> +	} else {
> +		tme_activate_cpu0 = tme_activate;
> +	}
> +
> +	if (!TME_ACTIVATE_LOCKED(tme_activate) ||
> !TME_ACTIVATE_ENABLED(tme_activate)) {
> +		pr_info_once("x86/tme: not enabled by BIOS\n");
> +		mktme_status = MKTME_DISABLED;
> +		return;
> +	}
> +
> +	if (mktme_status != MKTME_UNINITIALIZED)
> +		goto detect_keyid_bits;
> +
> +	pr_info("x86/tme: enabled by BIOS\n");
> +
> +	tme_policy = TME_ACTIVATE_POLICY(tme_activate);
> +	if (tme_policy != TME_ACTIVATE_POLICY_AES_XTS_128)
> +		pr_warn("x86/tme: Unknown policy is active:
> %#llx\n", tme_policy);
> +
> +	tme_crypto_algs = TME_ACTIVATE_CRYPTO_ALGS(tme_activate);
> +	if (!(tme_crypto_algs & TME_ACTIVATE_CRYPTO_AES_XTS_128)) {
> +		pr_err("x86/mktme: No known encryption algorithm is
> supported: %#llx\n",
> +				tme_crypto_algs);
> +		mktme_status = MKTME_DISABLED;
> +	}
> +detect_keyid_bits:
> +	keyid_bits = TME_ACTIVATE_KEYID_BITS(tme_activate);
> +	nr_keyids = (1UL << keyid_bits) - 1;
> +	if (nr_keyids) {
> +		pr_info_once("x86/mktme: enabled by BIOS\n");
> +		pr_info_once("x86/mktme: %d KeyIDs available\n",
> nr_keyids);
> +	} else {
> +		pr_info_once("x86/mktme: disabled by BIOS\n");
> +	}
> +
> +	if (mktme_status == MKTME_UNINITIALIZED) {
> +		/* MKTME is usable */
> +		mktme_status = MKTME_ENABLED;
> +	}
> +
> +	/*
> +	 * Exclude KeyID bits from physical address bits.
> +	 *
> +	 * We have to do this even if we are not going to use KeyID
> bits
> +	 * ourself. VM guests still have to know that these bits are
> not usable
> +	 * for physical address.
> +	 */
> +	c->x86_phys_bits -= keyid_bits;

It seems setup_pku() will call get_cpu_cap to restore c->x86_phys_bits
later? In which case I think you need to change setup_pku as well.

And for the comments here, I think it can be refined. It is true that
VM guest needs to know bits of physical address, but this info is not
used only by VM. I think the reason we need to update is this is simply
the fact.

Thanks,
-Kai

> +}
> +
>  static void init_intel_energy_perf(struct cpuinfo_x86 *c)
>  {
>  	u64 epb;
> @@ -680,6 +767,9 @@ static void init_intel(struct cpuinfo_x86 *c)
>  	if (cpu_has(c, X86_FEATURE_VMX))
>  		detect_vmx_virtcap(c);
>  
> +	if (cpu_has(c, X86_FEATURE_TME))
> +		detect_tme(c);
> +
>  	init_intel_energy_perf(c);
>  
>  	init_intel_misc_features(c);